The invention relates to a piezoelectric device for moving a fluid and having information feedback capability.
The use of fans for establishing a cooling air circulation in a housing of a portable electronic device is well known in the art. Typically, such fans have comprised piezoelectric fans or rotary type fans. For example, U.S. Pat. No. 5,861,703 describes an axial flow piezoelectric fan wherein a single fan blade is disposed in a housing having an axial flow passage with an inlet an outlet for cooling air. The fan blade carries a piezoelectric element that is electrically actuated to cause the fan blade to vibrate in the housing in a manner that cooling air is drawn in the inlet, flows axially through the air flow passage generally parallel to the housing wall and blade, and is discharged as an axially-flowing air stream from the outlet.
An object of the present invention is to provide a piezoelectric device amd method having information feedback capability that may be used to control operation of the device.
The present invention provides a piezoelectric device, such as a piezoelectric fan, pump, or microjet generator, and method for moving a fluid comprising a movable member having a first piezoelectric (PZT) actuator element coupled thereto to drive or actuate the movable member to move the fluid and a second piezoelectric (PZT) sensing element coupled thereto to provide feedback information (signals) related to a fluid parameter such as, for example, fluid viscosity, fluid density and/or fluid temperature. The second PZT element also can be used to drive the movable member in conjunction with the first PZT element. The feedback information can be used by a controller to control operation of the piezoelectric device.